TWI874416B - Adhesive Sheets and Optical Laminates - Google Patents

Abstract

[Topic] To provide an adhesive sheet and an optical laminate having excellent uniformity of light diffusion and excellent step compliance. [Solution] The adhesive sheet 1 includes a composite adhesive layer 11 having a light diffusion adhesive layer 111 containing light diffusion particles and a transparent adhesive layer 112 not containing light diffusion particles, wherein at least one of the light diffusion adhesive layer 111 and the transparent adhesive layer 112 is composed of an active energy ray-curable adhesive.

Description

Adhesive Sheets and Optical Laminates

The present invention relates to an adhesive sheet with light diffusion property and an optical laminate obtained by using the adhesive sheet.

In recent years, various mobile electronic devices such as smartphones and tablet computers include displays that use display modules including liquid crystal elements, light-emitting diodes (LED elements), organic electroluminescent (organic EL) elements, and most of these displays are used as touch panels.

In the display as described above, adhesive is sometimes used, for example, to bond the display module to a protective panel for protection thereof, or to bond the display module to a backlight system for illumination thereof.

Here, when the protective panel and the display module are attached to each other using an adhesive, there may be a frame-shaped printed layer with a step difference on the side of the protective panel facing the display module. In this case, if the adhesive layer does not conform to the step difference, the adhesive layer will float near the step difference, thereby causing reflection loss of light. Therefore, the above-mentioned adhesive layer needs to have step difference compliance. In addition, other parts of the display may also require this step difference compliance.

In order to solve the above problems, Patent Document 1 discloses an adhesive layer having a shear storage modulus (G') of 1.0×10 ⁵ Pa or less at 25°C and 1 Hz and a gel fraction of 40% or more. This adhesive layer improves the step compliance by reducing the storage modulus at room temperature. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Publication No. 2010-97070

[The problem that the invention is trying to solve]

On the other hand, in a display using a backlight system, there is a problem of uneven brightness (brightness unevenness) caused by the light source of the backlight. In order to solve this problem, a light diffusion plate is provided.

Here, from the perspective of reducing the components of the display to achieve thinness and low cost, or from the perspective of enhancing light diffusion, it is possible to consider using a light diffusing adhesive layer to replace the above-mentioned light diffusing plate, or to use it in combination with the above-mentioned light diffusing plate. This light diffusing adhesive layer can be obtained by adding light diffusing particles to the adhesive layer to increase the haze value. However, in this light diffusing adhesive layer, the higher the haze value, the higher the storage modulus, and the lower the adhesion. Therefore, this light diffusing adhesive layer may have a problem of reduced step compliance. Furthermore, the problem of reduced uniformity of light diffusion due to the step may also occur.

The present invention is completed in view of the above situation, and its purpose is to provide an adhesive sheet and an optical multilayer body with excellent uniformity of light diffusion and excellent step compliance. [Means for solving the problem]

In order to achieve the above-mentioned object, first, the present invention provides an adhesive sheet, which includes a composite adhesive layer having a light-diffusing adhesive layer containing light-diffusing particles and a transparent adhesive layer not containing light-diffusing particles, wherein at least one of the light-diffusing adhesive layer and the transparent adhesive layer is composed of an active energy ray-curable adhesive (Invention 1).

According to the adhesive sheet of the above invention (Invention 1), a transparent adhesive layer that does not contain light-diffusing particles can be brought into contact with and attached to an adherend having a step difference. In this way, the light-diffusing adhesive layer can be suppressed from being compressed or deformed due to the step difference of the adherend, so as to maintain the uniformity of light diffusion of the light-diffusing adhesive layer and further the composite adhesive layer. Furthermore, since the elastic modulus of the transparent adhesive layer is lower than that of the light-diffusing adhesive layer and flexibility can be maintained, the composite adhesive layer can be easily adapted to the step difference of the adherend by bringing the transparent adhesive layer into contact with and attaching the adherend having a step difference. Therefore, the initial step compliance is excellent, and after being hardened by active energy rays, it also has excellent step compliance under high temperature and high humidity conditions.

In the above invention (Invention 1), the haze value of the composite adhesive layer is preferably 40% or more and 99% or less (Invention 2).

In the above inventions (Inventions 1-2), the storage modulus G1 of the composite adhesive layer at 23° C. is preferably not less than 0.001 MPa and not more than 0.2 MPa (Invention 3).

In the above inventions (Inventions 1 to 3), the storage modulus G2 of the composite adhesive layer at 23° C. after irradiation with active energy rays is preferably not less than 0.08 MPa and not more than 10 MPa (Invention 4).

In the above inventions (Inventions 1 to 4), the storage modulus change rate ΔG' is the ratio of the storage modulus G2 of the aforementioned composite adhesive layer at 23°C after irradiation with active energy rays to the storage modulus G1 of the aforementioned composite adhesive layer at 23°C, and is preferably greater than 1.1 and less than 100 (Invention 5).

In the above inventions (Inventions 1 to 5), the adhesive force of the transparent adhesive layer in the adhesive sheet to the sodium calcium glass is preferably not less than 20 N/25 mm and not more than 80 N/25 mm (Invention 6).

In the above inventions (Inventions 1 to 6), the adhesive force of the transparent adhesive layer in the adhesive sheet to sodium calcium glass after irradiation with active energy rays is preferably not less than 20 N/25 mm and not more than 80 N/25 mm (Invention 7).

In the above inventions (Inventions 1 to 7), the adhesion of the light diffusing adhesive layer in the adhesive sheet to the sodium calcium glass is preferably 1 N/25 mm or more and 60 N/25 mm or less (Invention 8).

In the above inventions (Inventions 1 to 8), the adhesive strength of the light diffusion adhesive layer in the adhesive sheet to sodium calcium glass after irradiation with active energy rays is preferably 10 N/25 mm or more and 60 N/25 mm or less (Invention 9).

In the above inventions (Inventions 1 to 9), the thickness of the composite adhesive layer is preferably not less than 20 μm and not more than 1000 μm (Invention 10).

In the above inventions (Inventions 1 to 10), the thickness of the light diffusion adhesive layer is preferably not less than 10 μm and not more than 500 μm (Invention 11).

In the above inventions (Inventions 1 to 11), the thickness of the transparent adhesive layer is preferably not less than 10 μm and not more than 500 μm (Invention 12).

In the above inventions (Inventions 1 to 12), it is preferred that two release sheets are included and the composite adhesive layer is sandwiched between the release sheets and contacts the release surfaces of the two release sheets (Invention 13).

Secondly, the present invention provides an optical laminate, which includes an optical component, another optical component, and a cured composite adhesive layer for bonding the optical component and the other optical component to each other, wherein the cured composite adhesive layer is obtained by curing the composite adhesive layer of the adhesive sheet (Inventions 1 to 13) with active energy rays (Invention 14).

In the above invention (Invention 14), at least one of the optical component and the other optical component has a concave-convex surface on the side bonded by the cured composite adhesive layer, and the transparent adhesive layer of the cured composite adhesive layer is preferably in contact with the concave-convex surface (Invention 15). [Effect of the invention]

The adhesive sheet of the present invention has a sufficiently uniform light diffusion property and excellent step compliance. Furthermore, the optical multilayer body of the present invention has excellent step compliance and brightness non-uniformity suppression.

The following is a description of an embodiment of the present invention. [Adhesive sheet] According to an embodiment of the present invention, an adhesive sheet includes a composite adhesive layer having a light-diffusing adhesive layer containing light-diffusing particles and a transparent adhesive layer not containing light-diffusing particles. Moreover, at least one of the light-diffusing adhesive layer and the transparent adhesive layer is composed of an active energy ray-curable adhesive. In addition, in this specification, the so-called "active energy ray-curable adhesive" refers to an adhesive that can be cured by irradiation with active energy rays. Therefore, an already cured adhesive that cannot be further cured by irradiation with conventional active energy rays is not included in the "active energy ray-curable adhesive".

In the above-mentioned composite adhesive layer, there may be two or more transparent adhesive layers. In this case, it is preferred that at least one transparent adhesive layer is located on the surface in contact with the adherend (especially an adherend with a step difference (convex and concave)). Furthermore, there may be two or more light diffusion adhesive layers, and the outermost layer on at least one side of the composite adhesive layer is a transparent adhesive layer. Furthermore, from the perspective of controlling the haze value of the composite adhesive layer, it is preferred that there is one light diffusion adhesive layer.

When the light-diffusing adhesive layer containing light-diffusing particles is brought into contact with and conforms to the step (convexo-concave) of the adherend, the light-diffusing adhesive layer is compressed or deformed by the step of the adherend. As a result, the density of the light-diffusing particles in the light-diffusing adhesive layer becomes uneven, which impairs the uniformity of light diffusion. According to the adhesive sheet of this embodiment, a transparent adhesive layer not containing light-diffusing particles can be brought into contact with and attached to an adherend having a step. This can prevent the light diffusing adhesive layer from being compressed or deformed due to the step difference of the adherend, thereby maintaining the uniformity of light diffusion of the light diffusing adhesive layer and the composite adhesive layer. An optical multilayer body (display body) having excellent brightness unevenness suppression can be obtained based on the composite adhesive layer having uniform light diffusing properties (the composite adhesive layer after curing).

Furthermore, the light-diffusing adhesive layer containing light-diffusing particles tends to have a high elastic modulus and low flexibility, and thus the conformity to an adherend having a step (convex and concave) is easily reduced. According to the adhesive sheet of this embodiment, a transparent adhesive layer that does not contain light-diffusing particles can be brought into contact with and attached to an adherend having a step. Therefore, the composite adhesive layer easily conforms to the step, and the occurrence of bubbles or floating near the step can be suppressed. Moreover, after a component having a step (e.g., a glass plate) is bonded to another component (e.g., a glass plate) using the composite adhesive layer, the composite adhesive layer is hardened by irradiation with active energy rays to form a hardened composite adhesive layer. Thus, a laminate formed by bonding two components by a cured composite adhesive layer can be obtained. Even if the laminate is placed under high temperature and high humidity conditions, for example, at 85°C and 85% RH for 72 hours, bubbles, floating, or peeling near the step can be suppressed. That is, the adhesive sheet according to this embodiment has excellent initial step compliance and step compliance under high temperature and high humidity conditions.

Furthermore, since the light diffusion adhesive layer containing light diffusion particles is easy to reduce its adhesive force, when it is attached to a component that outgassing at high temperature or over time (such as a plastic plate), it is easy to cause bubbles, floating or peeling. According to the adhesive sheet of this embodiment, a transparent adhesive layer with high adhesive force and no light diffusion particles can be brought into contact with and attached to a component that outgassing. In the adhesive sheet according to this embodiment, it is preferred that either the transparent adhesive layer or the light diffusion adhesive layer is composed of an active energy ray-hardening adhesive, and it is preferred that the entire composite adhesive layer has active energy ray-hardening properties. In these cases, after the composite adhesive layer is attached to the adherend, the composite adhesive layer is hardened by irradiation with active energy rays to form a hardened composite adhesive layer, thereby obtaining a hardened composite adhesive layer having excellent anti-blistering properties. For example, after a component that outgasses (e.g., a plastic plate) and another component (e.g., a glass plate) are bonded together using the composite adhesive layer, the composite adhesive layer is hardened by irradiation with active energy rays to form a hardened composite adhesive layer. In this way, a laminate formed by bonding two components together using the hardened composite adhesive layer can be obtained. Even if the laminate is placed under high temperature and high humidity conditions, for example, at 85°C and 85% RH for 72 hours, bubbling, floating or peeling at the interface between the cured composite adhesive layer and the adherend (especially plastic sheets) can be suppressed.

Here, when a thick film adhesive layer is formed using a solvent-based material, a plurality of adhesive layers are usually stacked to form the adhesive layer. When a plurality of light diffusion adhesive layers are stacked to obtain an adhesive layer having a desired haze value (especially a high haze value), if the haze value of each light diffusion adhesive layer deviates from the target haze value, when the plurality of light diffusion adhesive layers are stacked, the deviation from the target haze value increases, and it becomes impossible to obtain an adhesive layer having the desired haze value. Therefore, there is a problem that the manufacturing yield is easily reduced. In contrast, by using a light-diffusing adhesive layer and a transparent adhesive layer as in the adhesive sheet according to the present embodiment, the number of light-diffusing adhesive layers (preferably one layer) can be reduced, and the thickness can be increased by using the transparent adhesive layer. In this way, an adhesive layer (composite adhesive layer) having a desired haze value can be easily and stably obtained, thereby improving the stability of the product.

The haze value of the composite adhesive layer of the adhesive sheet according to the present embodiment (value measured according to JIS K7136:2000) is preferably 40% or more, more preferably 50% or more, particularly preferably 60% or more, and more preferably 80% or more. In this way, it is easy to obtain good light diffusion and thus good brightness non-uniformity prevention. On the other hand, from the perspective of visibility of the optical laminate (display), the haze value of the composite adhesive layer is preferably 99% or less, more preferably 98% or less, particularly preferably 97% or less, and more preferably 96% or less. In addition, the haze value of the composite adhesive layer does not change substantially before and after irradiation with active energy rays.

The total light transmittance of the composite adhesive layer of the adhesive sheet according to the present embodiment (value measured according to JIS K7361-1:1997) is preferably 70% or more, particularly preferably 90% or more, and more preferably 99% or more. By setting the total light transmittance of the composite adhesive layer to the above value, the visibility as an optical laminate (display) becomes good. On the other hand, the upper limit of the total light transmittance of the composite adhesive layer is not particularly limited, and is usually 100% or less. In addition, the total light transmittance of the composite adhesive layer does not change substantially before and after the active energy ray irradiation.

From the perspective of the step compliance under high temperature and high humidity conditions, the storage modulus G1 of the composite adhesive layer of the adhesive sheet according to this embodiment at 23°C is preferably 0.001MPa or more, preferably 0.01MPa. It is particularly preferably 0.02MPa or more, and more preferably 0.04MPa or more. Furthermore, the above storage modulus G1 is preferably 0.2MPa or less, preferably 0.1MPa or less, particularly preferably 0.09MPa or less, and more preferably 0.08MPa or less. In this way, the initial step compliance becomes more excellent. In addition, the storage modulus in this manual is a value measured by a torsional shear method at a measurement frequency of 1Hz according to JIS K7244-6. Specifically, as described in the test examples below.

The storage modulus G2 of the composite adhesive layer of the adhesive sheet according to this embodiment at 23°C after irradiation with active energy rays is preferably 0.08 MPa or more, more preferably 0.09 MPa or more, particularly preferably 0.10 MPa or more, and more preferably 0.11 MPa or more. In this way, the step compliance under high temperature and high humidity conditions becomes more excellent. Furthermore, the storage modulus G2 is preferably 10 MPa or less, preferably 5 MPa or less, particularly preferably 1 MPa or less, and more preferably 0.2 MPa or less. In this way, good adhesion can be shown, and the adhesion to the adherend becomes more excellent. In addition, "after irradiation with active energy rays" means after irradiation with active energy rays at the same irradiation amount as the irradiation amount of active energy rays to which the active energy ray-curable adhesive layer (composite adhesive layer) is irradiated when it is set in the product. In this specification, the irradiation amount of active energy rays shown in Test Example 1 is used as a reference, but it is not limited to this.

The storage modulus variation rate ΔG', which is the ratio of the storage modulus G2 to the storage modulus G1 (storage modulus G2/storage modulus G1), is preferably 1.1 or more, more preferably 1.2 or more, particularly preferably 1.4 or more, and more preferably 1.8 or more. Furthermore, the storage modulus variation rate ΔG' is preferably 100 or less, more preferably 10 or less, particularly preferably 5 or less, and more preferably 2.5 or less. By setting the storage modulus variation rate ΔG' within the above range, the initial step compliance and the step compliance under high temperature and high humidity conditions can be made more excellent.

From the viewpoint of stably maintaining the light-diffusing fine particles in the light-diffusing adhesive layer, the light-diffusing adhesive layer according to the present embodiment has a storage modulus GD1 of 0.001 MPa or more at 23°C, preferably 0.01 MPa or more, particularly preferably 0.02 MPa or more, and more preferably 0.04 MPa or more. Furthermore, the storage modulus GD1 is preferably 0.2 MPa or less, preferably 0.16 MPa or less, particularly preferably 0.12 MPa or less, and more preferably 0.09 MPa or less. In this way, good adhesion with the transparent adhesive layer can be ensured.

When the light diffusion adhesive layer is composed of an active energy ray-curable adhesive, from the viewpoint of blister resistance, the storage modulus GD2 of the light diffusion adhesive layer at 23°C after irradiation with active energy rays is preferably 0.08 MPa or more, more preferably 0.10 MPa or more, particularly preferably 0.12 MPa or more, and more preferably 0.15 MPa or more. Furthermore, the storage modulus GD2 is preferably 10 MPa or less, preferably 5 MPa or less, particularly preferably 1 MPa or less, and more preferably 0.3 MPa or less. In this way, good adhesion can be exhibited, and the bonding property with the adherend becomes more excellent.

The storage modulus variation rate ΔGD', which is the ratio of the storage modulus GD2 to the storage modulus GD1 (storage modulus GD2/storage modulus GD1), is preferably 1.1 or more, more preferably 1.4 or more, particularly preferably 1.8 or more, and more preferably 2.1 or more. Furthermore, the storage modulus variation rate ΔGD' is preferably 100 or less, more preferably 10 or less, particularly preferably 5 or less, and more preferably 3 or less. By setting the storage modulus variation rate ΔGD within the above range, a good balance between maintaining adhesion after curing and blister resistance can be achieved.

From the perspective of the step compliance under high temperature and high humidity conditions, the storage modulus GT1 of the transparent adhesive layer according to this embodiment at 23°C is preferably 0.001 MPa or more, more preferably 0.01 MPa or more, particularly preferably 0.02 MPa or more, and more preferably 0.04 MPa or more. Furthermore, the storage elastic modulus GT1 is preferably 0.2 MPa or less, preferably 0.1 MPa or less, particularly preferably 0.09 MPa or less, and more preferably 0.08 MPa or less. In this way, the initial step compliance becomes more excellent.

In the case where the transparent adhesive layer is composed of an active energy ray-hardening adhesive, the storage modulus GT2 of the transparent adhesive layer at 23°C after irradiation with active energy rays is preferably 0.08 MPa or more, more preferably 0.09 MPa or more, particularly preferably 0.10 MPa or more, and more preferably 0.11 MPa or more. In this way, the step compliance under high temperature and high humidity conditions becomes more excellent. Furthermore, the above storage modulus GT2 is preferably 10 MPa or less, preferably 5 MPa or less, particularly preferably 1 MPa or less, and more preferably 0.2 MPa or less. In this way, good adhesion can be shown, and the bonding between the adherend becomes more excellent.

The storage modulus variation rate ΔGT, which is the ratio of the storage modulus GT2 to the storage modulus GT1 (storage modulus GT2/storage modulus GT1), is preferably 1.1 or more, more preferably 1.2 or more, particularly preferably 1.6 or more, and more preferably 1.8 or more. Furthermore, the storage modulus variation rate ΔGT is preferably 100 or less, more preferably 10 or less, particularly preferably 5 or less, more preferably 3 or less, and more preferably 2.5 or less. By setting the storage modulus variation rate ΔGT within the above range, the initial step compliance and the step compliance under high temperature and high humidity conditions can be made more excellent.

From the perspective of the step compliance under high temperature and high humidity conditions, the gel fraction of the composite adhesive layer of the adhesive sheet according to this embodiment is preferably 20% or more, more preferably 30% or more, particularly preferably 40% or more, and more preferably 50% or more. Furthermore, the gel fraction is preferably 80% or less, more preferably 70% or less, particularly preferably 65% or less, and more preferably 60% or less. In this way, the initial step compliance becomes more excellent. In addition, in this specification, the method for measuring the gel fraction of the adhesive is described in the test example described later.

The gel fraction of the composite adhesive layer of the adhesive sheet according to this embodiment after irradiation with active energy rays is preferably 40% or more, more preferably 50% or more, particularly preferably 60% or more, and more preferably 65% or more. In this way, the step compliance under high temperature and high humidity conditions becomes more excellent. Furthermore, the gel fraction is preferably 99% or less, more preferably 89% or less, particularly preferably 80% or less, and more preferably 75% or less. In this way, good adhesion can be shown, and the adhesion to the adherend becomes more excellent.

From the viewpoint of maintaining the dispersion state of the light diffusion particles and effectively exerting the brightness unevenness suppression property, the gel fraction of the light diffusion adhesive layer according to this embodiment is preferably 30% or more, more preferably 40% or more, particularly preferably 50% or more, and more preferably 55% or more. Furthermore, the gel fraction is preferably 90% or less, more preferably 80% or less, particularly preferably 70% or less, and more preferably 65% or less. In this way, good adhesion with the transparent adhesive layer can be ensured.

When the light diffusion adhesive layer is composed of an active energy ray-curable adhesive, from the viewpoint of blister resistance, the gel fraction of the light diffusion adhesive layer after irradiation with active energy rays is preferably 40% or more, more preferably 50% or more, particularly preferably 60% or more, and more preferably 65% or more. Furthermore, the gel fraction is preferably 99% or less, more preferably 90% or less, particularly preferably 85% or less, and more preferably 80% or less. In this way, good adhesion can be exhibited, and the bonding property with the adherend becomes more excellent.

From the perspective of step compliance under high temperature and high humidity conditions, the gel fraction of the transparent adhesive layer according to this embodiment is preferably 20% or more, more preferably 30% or more, particularly preferably 40% or more, and more preferably 50% or more. Furthermore, the gel fraction is preferably 80% or less, more preferably 70% or less, particularly preferably 60% or less, and more preferably 55% or less. In this way, the initial step compliance becomes more excellent.

In the case where the transparent adhesive layer is composed of an active energy ray-hardening adhesive, the gel fraction of the transparent adhesive layer after irradiation with active energy rays is preferably 40% or more, more preferably 50% or more, particularly preferably 60% or more, and more preferably 65% or more. In this way, the step compliance under high temperature and high humidity conditions becomes more excellent. Furthermore, the gel fraction is preferably 98% or less, more preferably 87% or less, particularly preferably 75% or less, and more preferably 70% or less. In this way, good adhesion can be exhibited, and the adhesion to the adherend becomes more excellent.

From the perspective of step compliance and operability under high temperature and high humidity conditions, the adhesive force of the transparent adhesive layer on the sodium calcium glass in the adhesive sheet according to this embodiment is preferably 20N/25mm or more, more preferably 30N/25mm or more, particularly preferably 35N/25mm or more, and more preferably 40N/25mm or more. Furthermore, the above-mentioned adhesive force is preferably 80N/25mm or less, preferably 70N/25mm or less, particularly preferably 60N/25mm or less, and more preferably 50N/25mm or less. In this way, good reworkability can be obtained, and the adherend can be reused even in the event of a bonding error.

According to the adhesive sheet of this embodiment, the adhesive force of the transparent adhesive layer to the sodium calcium glass after irradiation with active energy rays is preferably 20N/25mm or more, more preferably 30N/25mm or more, particularly preferably 40N/25mm or more, and more preferably 45N/25mm or more. In this way, the step compliance under high temperature and high humidity conditions becomes more excellent. Furthermore, the above-mentioned adhesive force is preferably 80N/25mm or less, preferably 70N/25mm or less, particularly preferably 60N/25mm or less, and more preferably 50N/25mm or less. In this way, good heavy workability can be obtained.

From the perspective of operability, the adhesive force of the light diffusion adhesive layer on the sodium calcium glass in the adhesive sheet according to this embodiment is preferably 1N/25mm or more, more preferably 4N/25mm or more, particularly preferably 8N/25mm or more, and more preferably 13N/25mm or more. Furthermore, the above-mentioned adhesive force is preferably 60N/25mm or less, preferably 50N/25mm or less, particularly preferably 40N/25mm or less, and more preferably 35N/25mm or less. In this way, good reworkability can be obtained, and the adherend can be reused even in the event of a bonding error.

According to the adhesive sheet of this embodiment, the adhesion of the light diffusion adhesive layer to the sodium calcium glass after irradiation with active energy rays is preferably 10N/25mm or more, preferably 15N/25mm or more, particularly preferably 20N/25mm or more, and more preferably 25N/25mm or more. In this way, the blister resistance becomes more excellent. Furthermore, the above-mentioned adhesion is preferably 60N/25mm or less, preferably 50N/25mm or less, particularly preferably 45N/25mm or less, and more preferably 40N/25mm or less. In this way, good reworkability can be obtained.

Here, the adhesion in this specification is basically the adhesion measured by the 180-degree peeling method according to JIS Z0237:2009, wherein the measurement sample has a width of 25 mm and a length of 100 mm. This measurement sample is attached to the adherend and pressurized at 0.5 MPa and 50°C for 20 minutes, then placed under normal pressure, 23°C, and 50% RH for 24 hours, and then measured at a peeling speed of 300 mm/min to obtain the above-mentioned adhesion.

The thickness of the composite adhesive layer of the adhesive sheet according to this embodiment is preferably 20 μm or more, preferably 40 μm or more, particularly preferably 60 μm or more, and more preferably 80 μm or more. In this way, the end difference (concave and convex) of the adherend can be well filled, so that the step compliance becomes more excellent. Furthermore, the thickness of the composite adhesive layer is preferably 1000 μm or less, preferably 800 μm or less, particularly preferably 400 μm or less, and more preferably 200 μm or less. In this way, the processability becomes good, and appearance defects caused by embossing and the like are almost not likely to occur.

The thickness of the light diffusion adhesive layer of the adhesive sheet according to this embodiment is preferably 10 μm or more, preferably 20 μm or more, particularly preferably 30 μm or more, and more preferably 40 μm or more. In this way, it is easy to obtain the desired light diffusion or haze value, and it is also easy to obtain the desired adhesion. Furthermore, the thickness of the light diffusion adhesive layer is preferably 500 μm or less, preferably 400 μm or less, particularly preferably 200 μm or less, and more preferably 100 μm or less. In this way, it is easy to obtain the desired light diffusion or haze value, and the processability is also improved.

According to the adhesive sheet of this embodiment, the thickness of the transparent adhesive layer on the surface in contact with the step (convex and concave) of the adherend is preferably greater than the height of the step of the adherend. In this way, the step of the adherend can be absorbed by the transparent adhesive layer, and the light diffusion adhesive layer can be more effectively suppressed from being compressed or deformed due to the step. Therefore, the uniformity of light diffusion in the light diffusion adhesive layer (composite adhesive layer) becomes higher.

Specifically, the thickness of the transparent adhesive layer according to this embodiment is preferably 10 μm or more, more preferably 20 μm or more, particularly preferably 30 μm or more, and more preferably 40 μm or more. In this way, the uniformity of light diffusion in the composite adhesive layer, the step compliance under high temperature and high humidity conditions, and the blister resistance become more excellent. On the other hand, the thickness of the transparent adhesive layer is preferably 500 μm or less, more preferably 400 μm or less, particularly preferably 200 μm or less, and more preferably 100 μm or less. In this way, the processability becomes good, and appearance defects caused by embossing and the like are almost not likely to occur. In addition, when the transparent adhesive layer has a plurality of layers as shown in FIG. 4 described later, the above thickness refers to the thickness of one transparent adhesive layer.

The composite adhesive layer is preferably used to bond one optical component to another optical component. The optical component will be described later. In the optical laminate (display) obtained by using the composite adhesive layer of the adhesive sheet according to this embodiment, the light diffusion property of the composite adhesive layer becomes uniform, so that the brightness unevenness of the optical laminate (display) can be suppressed. However, the adhesive sheet according to this embodiment is not limited to the use of optical laminates or displays.

FIG1 shows a specific structure of an example of an adhesive sheet according to the present embodiment. As shown in FIG1 , the adhesive sheet 1 is composed of two peeling sheets 12a and 12b, and a composite adhesive layer 11 sandwiched between the two peeling sheets 12a and 12b and contacting the peeling surfaces of the two peeling sheets 12a and 12b. In addition, in this specification, the peeling surface of the peeling sheet means a surface having peeling properties in the peeling sheet, and also includes any of a surface subjected to peeling treatment and a surface that can exhibit peeling properties without peeling treatment.

The composite adhesive layer 11 of this embodiment is a laminate of a light diffusion adhesive layer 111 and a transparent adhesive layer 112. However, the present invention is not limited thereto. The transparent adhesive layer 112 is preferably located on the surface of the adhesive layer 11 that contacts the step of the adherend.

1. Each component 1-1. Composite adhesive layer The light-diffusing adhesive layer 111 is preferably composed of an adhesive containing light-diffusing particles. On the other hand, the transparent adhesive layer 112 is preferably composed of an adhesive that does not contain light-diffusing particles. In addition, the so-called "does not contain light-diffusing particles" means "basically does not contain light-diffusing particles", and in addition to the case where light-diffusing particles are completely not contained, it also includes the case where the content does not impair the effect of the present embodiment. This content is preferably 0.1% by mass or less, particularly preferably 0.01% by mass or less, more preferably 0.001% by mass or less, and the best is 0% by mass.

The type of adhesive constituting the light diffusion adhesive layer 111 and the transparent adhesive layer 112 of the adhesive sheet 1 according to the present embodiment is not particularly limited as long as at least one layer of the light diffusion adhesive layer 111 and the transparent adhesive layer 112 is composed of an active energy ray-hardening adhesive. For example, it can be any one of an acrylic adhesive, a polyester adhesive, a polyurethane adhesive, a rubber adhesive, a silicone adhesive, etc. Furthermore, the adhesive can be any one of an emulsion type, a solvent type, or a solvent-free type, and can also be any one of a crosslinked type or a non-crosslinked type. Among them, an acrylic adhesive having excellent adhesive properties and optical properties is preferred. As the acrylic adhesive, a crosslinking type is preferred, and a thermal crosslinking type is more preferred.

The adhesive constituting the light diffusion adhesive layer 111 and the adhesive constituting the transparent adhesive layer 112 may be of the same type or of different types, and it is preferred that both of them are active energy ray-hardening adhesives, especially active energy ray-hardening acrylic adhesives. In this way, excellent blister resistance can be exhibited. In this case, the components other than the light diffusion particles may be the same or different. Furthermore, the monomer components of the main polymer may be the same or different. In addition, the adhesive constituting the light diffusion adhesive layer 111 and the adhesive constituting the transparent adhesive layer 112 may be one of them being an active energy ray-hardening acrylic adhesive and the other being an active energy ray-non-hardening acrylic adhesive.

The following description will focus on the case where both the adhesive constituting the light diffusion adhesive layer 111 and the adhesive constituting the transparent adhesive layer 112 are active energy ray-curable acrylic adhesives, but the present invention is not limited thereto.

From the viewpoint of increasing the cohesive force between polymers, the adhesive constituting the light diffusion adhesive layer 111 and the adhesive constituting the transparent adhesive layer 112 are preferably formed by crosslinking an adhesive composition containing a (meth)acrylate polymer (A), a crosslinking agent (B), and an active energy ray-hardening component (C) (hereinafter sometimes referred to as "adhesive composition P"). In the case of the light diffusion adhesive layer 111, the adhesive composition P further contains light diffusion particles (D). As long as the adhesive composition P having the above components is used, the above storage modulus, gel fraction, haze value, and adhesion, etc. can be easily satisfied.

The adhesive obtained from the adhesive composition P can show excellent optical properties, adhesion, step compliance, etc. In addition, in this specification, the so-called (meth) acrylic acid means both acrylic acid and methacrylic acid. The same is true for other similar terms. Furthermore, "polymer" also includes the concept of "copolymer".

(1) Components of the adhesive composition (1-1) (Meth)acrylate polymer (A) The (meth)acrylate polymer (A) in this embodiment preferably includes a reactive group-containing monomer having a reactive group that reacts with a crosslinking agent (B) in the molecule as a monomer unit constituting the polymer. The reactive group derived from the reactive group-containing monomer reacts with the crosslinking agent (B) to form a crosslinked structure (three-dimensional network structure), thereby obtaining an adhesive having the desired cohesive force.

Preferred examples of the reactive group-containing monomer include monomers having a hydroxyl group in the molecule (hydroxyl-containing monomers), monomers having a carboxyl group in the molecule (carboxyl-containing monomers), and monomers having an amine group in the molecule (amine-containing monomers). Among them, hydroxyl-containing monomers or carboxyl-containing monomers are preferred because they have excellent reactivity with the crosslinking agent (B).

As the hydroxyl group-containing monomer, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate can be cited. Among them, hydroxyalkyl (meth)acrylates having a hydroxyalkyl group having 1 to 4 carbon atoms are preferred, considering the reactivity of the hydroxyl group in the obtained (meth)acrylate polymer (A) with the crosslinking agent (B) and the copolymerizability with other monomers. Specifically, for example, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate can be cited as preferred, and 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate can be cited as particularly preferred. The above materials may be used alone or in combination of two or more.

Examples of carboxyl group-containing monomers include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and liraconic acid. Of these, acrylic acid is preferred in view of the reactivity of the carboxyl group in the obtained (meth)acrylate polymer (A) with the crosslinking agent (B) and copolymerizability with other monomers. The above materials may be used alone or in combination of two or more.

As the amine-containing monomer, for example, aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, etc. can be listed. The above materials can be used alone or in combination of two or more. In addition, this amine-containing monomer excludes the nitrogen-containing monomer described later.

In the (meth)acrylate polymer (A), the lower limit of the content of the reactive group-containing monomer as a monomer unit constituting the polymer is preferably 5 mass % or more, particularly preferably 10 mass % or more, and more preferably 15 mass % or more. Furthermore, in the (meth)acrylate polymer (A), the upper limit of the content of the reactive group-containing monomer as a monomer unit constituting the polymer is preferably 40 mass % or less, particularly preferably 30 mass % or less, and more preferably 25 mass % or less. When the (meth)acrylate polymer (A) contains the reactive group-containing monomer as a monomer unit in the above content, a good cross-linking structure is formed in the obtained adhesive, and it becomes easy to obtain the desired gel fraction and storage modulus. Furthermore, when the light diffusing fine particles (D) are contained, the dispersibility of the light diffusing fine particles (D) in the obtained adhesive tends to be good.

Furthermore, it is also preferred that the (meth)acrylate polymer (A) does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer. Since the carboxyl group is an acid component, by not containing a carboxyl group-containing monomer, it is possible to suppress defects caused by the acid on the object to which the adhesive is attached, for example, even in the presence of a transparent conductive film such as tin-doped indium oxide (ITO) or a metal film, it is possible to suppress those problems caused by the acid (corrosion, resistance value change, etc.). However, it is permissible to contain a predetermined amount of carboxyl group-containing monomer to the extent that the above-mentioned defects are not generated. Specifically, in the (meth)acrylate polymer (A), the content of the carboxyl group-containing monomer as a monomer unit is allowed to be 0.1% by mass or less, preferably 0.01% by mass or less, and more preferably 0.001% by mass.

The (meth)acrylate polymer (A) preferably contains an alkyl (meth)acrylate as a monomer unit constituting the polymer. In this way, good adhesion can be exhibited and the storage modulus of the resulting adhesive can be reduced. The alkyl group may be linear or branched.

As the alkyl (meth)acrylate, from the viewpoint of adhesion, an alkyl (meth)acrylate having an alkyl group with 1 to 20 carbon atoms is preferred. As the alkyl (meth)acrylate having an alkyl group with 1 to 20 carbon atoms, for example, there can be listed methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, N-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, N-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, and the like. Among them, from the viewpoint of further improving adhesion or reducing storage modulus, (meth)acrylates having an alkyl group with 4 to 8 carbon atoms are preferred, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, or isooctyl (meth)acrylate are particularly preferred, and n-butyl acrylate, 2-ethylhexyl acrylate, or isooctyl acrylate is more preferred. In addition, the above materials may be used alone or in combination of two or more.

In the (meth)acrylate polymer (A), the content of the (meth)acrylate alkyl ester as a monomer unit constituting the polymer is preferably 45 mass % or more, particularly preferably 55 mass % or more, and more preferably 65 mass % or more. When the lower limit of the content of the (meth)acrylate alkyl ester is the above value, the (meth)acrylate polymer (A) can exhibit appropriate adhesion. Furthermore, when the light diffusion particles (D) are contained, the dispersibility of the light diffusion particles (D) in the adhesive is good enough to suppress the damage to the desired adhesion of the (meth)acrylate polymer (A). On the other hand, in the (meth)acrylate polymer (A), the content of the (meth)acrylate alkyl ester as a monomer unit constituting the polymer is preferably 99 mass % or less, more preferably 95 mass % or less, particularly preferably 90 mass % or less, and even more preferably 75 mass % or less. When the upper limit of the content of the (meth)acrylate alkyl ester is the above value, other monomer components such as a monomer having a reactive functional group can be introduced into the (meth)acrylate polymer (A) in an appropriate amount.

In the above-mentioned (meth)acrylate polymer (A), it is preferred that a monomer having an alicyclic structure (alicyclic structure-containing monomer) is contained in the molecule as a monomer unit constituting the polymer. The alicyclic structure-containing monomer can increase the glass transition temperature of the polymer and increase the storage modulus of the obtained adhesive. Furthermore, since the volume of the alicyclic structure-containing monomer is large, it is speculated that the presence of the alicyclic structure-containing monomer in the polymer can increase the spacing between the polymers, thereby reducing the viscosity of the coating liquid, making it easier to increase the film thickness of the adhesive layer.

The carbon ring having an alicyclic structure in the alicyclic structure-containing monomer may be a saturated structure or may have a part of an unsaturated bond. Furthermore, the alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as a bicyclic or tricyclic alicyclic structure. From the viewpoint of increasing the storage modulus of the obtained adhesive and increasing the film thickness of the adhesive layer at the same time, the alicyclic structure is preferably a polycyclic alicyclic structure (polycyclic structure). Moreover, considering the mutual solubility between the (meth)acrylate polymer (A) and other components, the polycyclic structure is particularly preferably a bicyclic to tetracyclic structure. Furthermore, as described above, from the viewpoint of improving the storage modulus or increasing the film thickness, the number of carbon atoms in the alicyclic structure (meaning the total number of carbon atoms in the portion forming the ring, and when multiple rings are independent of each other, the total number of carbon atoms in their sum) is usually preferably 5 or more, and particularly preferably 7 or more. On the other hand, the upper limit of the number of carbon atoms in the alicyclic structure is not particularly limited, but from the same viewpoint as above, it is preferably 15 or less, and particularly preferably 10 or less.

As the above-mentioned alicyclic structure-containing monomer, specifically, cyclohexyl (meth)acrylate, dicyclopentyl (meth)acrylate, adhanyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, etc. can be listed. Among them, dicyclopentyl (meth)acrylate (the number of carbon atoms in the alicyclic structure is 10), adhanyl (meth)acrylate (the number of carbon atoms in the alicyclic structure is 10), or isobornyl acrylate (meth)acrylate (the number of carbon atoms in the alicyclic structure is 7) which can show better step compliance is preferred, isobornyl (meth)acrylate is particularly preferred, and isobornyl acrylate is more preferred. The above-mentioned materials can be used alone or in combination of two or more.

When the (meth)acrylate polymer (A) includes an alicyclic structure-containing monomer as a monomer unit constituting the polymer, the content of the alicyclic structure-containing monomer is preferably 1% by mass or more, particularly preferably 5% by mass or more, and more preferably 10% by mass or more, from the viewpoint of adjusting the storage modulus of the obtained adhesive to a preferred range. Furthermore, from the same viewpoint as above, the content of the alicyclic structure-containing monomer is preferably 25% by mass or less, particularly preferably 20% by mass or less, and more preferably 15% by mass or less.

Furthermore, the (meth)acrylate polymer (A) preferably contains a nitrogen-containing monomer as a monomer unit constituting the polymer. By having a nitrogen-containing monomer as a constituent unit in the polymer, a predetermined polarity can be imparted to the adhesive layer, and the adhesive layer also has excellent affinity for adherends having polarity such as glass. From the perspective of imparting appropriate rigidity to the (meth)acrylate polymer (A), the nitrogen-containing monomer is preferably a monomer having a nitrogen-containing heterocyclic ring. Furthermore, from the viewpoint of increasing the degree of freedom of the nitrogen-containing monomer-derived portion in the high-order structure of the adhesive to be constructed, it is preferred that the nitrogen-containing monomer does not contain a reactive unsaturated double bond group other than one polymerizable group used for polymerization to form the (meth)acrylate polymer (A).

As the monomer having a nitrogen-containing heterocyclic ring, for example, N-(methyl)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(methyl)acryloylpyrrolidone, N-(methyl)acryloylpiperidine, N-(methyl)acryloylpyrrolidine, N-(methyl)acryloylaziridine, (methyl)acrylic acid aziridinylethyl ester, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, N-vinylphthalimide, etc. can be listed. Among them, N-(methyl)acryloylmorpholine is preferred because it can exert a better adhesion, and N-acryloylmorpholine is particularly preferred. The above materials can be used alone or in combination of two or more.

When the (meth)acrylate polymer (A) includes a nitrogen atom-containing monomer as a monomer unit constituting the polymer, the content of the nitrogen atom-containing monomer is preferably 1 mass % or more, particularly preferably 2 mass % or more, and more preferably 4 mass % or more. Furthermore, in the (meth)acrylate polymer (A), the content of the nitrogen atom-containing monomer as a monomer unit constituting the polymer is preferably 24 mass % or less, particularly preferably 16 mass % or less, and more preferably 8 mass % or less. When the content of the nitrogen atom-containing monomer is within the above range, the obtained adhesive can sufficiently exhibit excellent adhesion to glass.

The (meth)acrylate polymer (A) may also include other monomers as monomer units constituting the polymer as required. As other monomers, monomers that do not contain reactive functional groups are preferred in order not to hinder the aforementioned effects of the monomers containing reactive functional groups. Examples of such monomers include (meth)acrylate alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, styrene, and the like. The above materials may be used alone or in combination of two or more.

The (meth)acrylate polymer (A) is preferably a linear polymer. Since it is a linear polymer, it is easy to generate molecular chain linkage, and it is expected that the cohesive force can be improved, so it is easy to obtain an adhesive with excellent step compliance and blister resistance under high temperature and high humidity conditions.

Furthermore, the (meth)acrylate polymer (A) is preferably a solution polymer obtained by solution polymerization. Since it is a solution polymer, it is easy to obtain a polymer with a high molecular weight, and it can be expected that the cohesive force can be improved, so it is easy to obtain an adhesive with excellent step compliance and blister resistance under high temperature and high humidity conditions.

The polymerization form of the (meth)acrylate polymer (A) may be a random copolymer or a block copolymer.

The weight average molecular weight of the (meth)acrylate polymer (A) is preferably 200,000 or more, more preferably 300,000 or more, and particularly preferably 400,000 or more. In this way, the storage modulus and gel fraction of the obtained adhesive can be improved, so that the step compliance under high temperature and high humidity conditions becomes more excellent. Furthermore, the weight average molecular weight is more preferably 500,000 or more. In this way, the adhesive containing the light diffusion particles (D) can also obtain a high storage modulus that can show sufficient cohesion. In addition, the dispersion performance of the light diffusion particles (D) in the adhesive is good enough.

Furthermore, the upper limit of the weight average molecular weight of the (meth)acrylate polymer (A) is preferably 1.5 million or less, more preferably 1.2 million or less, particularly preferably 1 million or less, and more preferably 800,000 or less. When the upper limit of the weight average molecular weight of the (meth)acrylate polymer (A) is the above value, the storage modulus of the obtained adhesive is likely to have an appropriate value, and the initial step compliance becomes more excellent. The weight average molecular weight in this specification is a value converted to standard polystyrene measured by gel permeation chromatography (GPC).

In the adhesive composition P, the (meth)acrylate polymer (A) may be used alone or in combination of two or more.

(1-2) Crosslinking agent (B) The crosslinking agent (B) mentioned above can be any crosslinking agent that can react with the reactive group of the (meth)acrylate polymer (A), for example, isocyanate crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, melamine crosslinking agents, aziridine crosslinking agents, hydrazine crosslinking agents, aldehyde crosslinking agents, oxazoline crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, ammonium salt crosslinking agents, etc. Among the above, it is preferred to use an isocyanate crosslinking agent having excellent reactivity to a hydroxyl group and a carboxyl group, or an epoxy crosslinking agent having excellent reactivity to a carboxyl group. In addition, the crosslinking agent (B) may be used alone or in combination of two or more.

Isocyanate crosslinking agents include at least polyisocyanate compounds. Examples of polyisocyanate compounds include aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and their biuret forms, isocyanurate forms, and adducts of reaction products with low molecular weight hydrogen-containing active compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trihydroxymethylpropane, and castor oil. Among them, from the viewpoint of reactivity with hydroxyl groups, trihydroxymethylpropane-modified aromatic polyisocyanates are preferably used, and trihydroxymethylpropane-modified toluene diisocyanate and trihydroxymethylpropane-modified xylene diisocyanate are particularly preferred.

Examples of epoxy crosslinking agents include 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylene diamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trihydroxymethylpropane diglycidyl ether, diglycidyl aniline, and diglycidyl amine. Among them, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane is preferred from the viewpoint of reactivity with carboxyl groups.

The content of the crosslinking agent (B) in the adhesive composition P is preferably 0.01 parts by mass or more, particularly 0.05 parts by mass or more, and more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the (meth)acrylate polymer (A). Furthermore, this content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, particularly preferably 1 part by mass or less, more preferably 0.4 parts by mass or less, and most preferably 0.2 parts by mass or less. Since the content of the crosslinking agent (B) is within the above range, the obtained adhesive easily has appropriate storage modulus, gel fraction, adhesion, etc.

(1-3) Active energy ray-hardening component (C) In the adhesive formed by crosslinking the adhesive composition P containing the active energy ray-hardening component (C), the active energy ray-hardening components (C) are polymerized with each other in the adhesive after being hardened by active energy ray. It can be inferred that the active energy ray-hardening component (C) after the polymerization is linked to the crosslinking structure (three-dimensional network structure) of the (meth)acrylate polymer (A). This adhesive with a high-level structure increases the storage modulus and gel fraction to a predetermined level, and the step compliance under high temperature and high humidity conditions becomes particularly excellent.

The active energy ray-curable component (C) is not particularly limited as long as it can be cured by irradiation with active energy rays to obtain the above-mentioned effects, and may be any of a monomer, an oligomer or a polymer, or a mixture thereof. Among them, multifunctional acrylate monomers having a more excellent anti-foaming property are preferred.

Examples of the multifunctional acrylate monomer include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, adipate neopentyl glycol di(meth)acrylate, hydroxy neopentyl glycol di(meth)acrylate, dicyclopentyl di(meth)acrylate, tricyclodecane dimethanol (meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphoric acid di(meth)acrylate, di(acryloyloxyethyl) isocyanurate, acrylated cyclohexyl di(meth)acrylate, ethoxylated bisphenol A diacrylate, 9,9-bis[4-(2-acryloyloxyethoxy)phenyl] ] fluorene and the like; trifunctional type of trihydroxymethylpropane tri(meth)acrylate, dipentatriol tri(meth)acrylate, propionic acid-modified dipentatriol tri(meth)acrylate, pentatriol tri(meth)acrylate, propylene oxide-modified trihydroxymethylpropane tri(meth)acrylate, 3-(acryloyloxyethyl)isocyanurate, ε-caprolactone-modified 3-(2-(meth)acryloyloxyethyl)isocyanurate and the like; quadrifunctional type of diglycerol tetra(meth)acrylate, pentatriol tetra(meth)acrylate and the like; pentafunctional type of propionic acid-modified dipentatriol penta(meth)acrylate and the like; hexafunctional type of dipentatriol hexa(meth)acrylate, caprolactone-modified dipentatriol hexa(meth)acrylate and the like. The above materials may be used alone or in combination of two or more. Furthermore, from the viewpoint of compatibility with the (meth)acrylate polymer (A), the molecular weight of the polyfunctional acrylate monomer is preferably less than 1,000.

From the viewpoint of setting the storage modulus value of the adhesive after active energy ray irradiation and the storage modulus change rate ΔG' before and after curing to appropriate values and making the step compliance under high temperature and high humidity conditions more excellent, the lower limit of the content of the active energy ray-curable component (C) in the adhesive composition P is preferably 1 part by mass or more, particularly preferably 3 parts by mass or more, and more preferably 4 parts by mass or more, relative to 100 parts by mass of the (meth)acrylate polymer (A). On the other hand, from the viewpoint of the adhesive force of the adhesive after active energy ray irradiation, the upper limit of the above content is preferably 20 parts by mass or less, particularly preferably 12 parts by mass or less, and more preferably 8 parts by mass or less.

(1-4) Light-diffusing particles (D) The light-diffusing particles (D) may be any particles that can make the light-diffusing adhesive layer 111 and the composite adhesive layer 11 satisfy the aforementioned physical properties.

As light diffusion particles (D), for example, inorganic particles such as silica, calcium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc, and titanium dioxide can be listed; organic light-transmitting particles such as acrylic resin, polystyrene resin, polyethylene resin, and epoxy resin; particles composed of silicon-containing compounds having a structure between inorganic and organic, such as silicone resin (for example, Tospearl series manufactured by Momentive Performance Materials Japan), etc. Among them, particles composed of silicone resin are preferred. In this way, the adhesive sheet becomes easy to meet the aforementioned haze value and image clarity. The above light diffusion fine particles (D) may be used alone or in combination of two or more.

As the shape of the light-diffusing particles (D), spherical particles with uniform light diffusion are preferred. The lower limit of the average particle size of the light-diffusing particles (D) obtained by the centrifugal sedimentation light transmission method is preferably 1.0 μm or more, particularly preferably 2.0 μm or more, and more preferably 3.0 μm or more. When the lower limit of the average particle size is the above value, it becomes easy to produce the desired haze. On the other hand, the upper limit of the average particle size is preferably 10 μm or less, particularly preferably 8 μm or less, and more preferably 6 μm or less. When the upper limit of the average particle size is the above value, it is easy to prevent the haze value from becoming too high, and a high-definition display image can be displayed well.

The average particle size obtained by the centrifugal sedimentation light transmission method was measured by using a centrifugal automatic particle size distribution measuring device (CAPA-700 manufactured by Horiba, Ltd.) by thoroughly stirring 1.2 g of fine particles and 98.8 g of isopropyl alcohol as a measurement sample.

The content of the light diffusing particles (D) in the adhesive composition P can be any amount that satisfies the aforementioned physical properties. Specifically, the content of the light diffusing particles (D) is preferably 1% by mass or more, more preferably 3% by mass or more, particularly preferably 6% by mass or more, and more preferably 8% by mass or more. Furthermore, the content of the light diffusing particles (D) is preferably 50% by mass or less, more preferably 40% by mass or less, particularly preferably 30% by mass or less, and more preferably 25% by mass or less. When the content of the light diffusing particles (D) is within the above range, the aforementioned haze value, storage modulus, and adhesion can be easily satisfied.

(1-5) Photopolymerization initiator (E) When ultraviolet rays are used as active energy rays for curing the adhesive composition P, the adhesive composition P preferably further includes a photopolymerization initiator (E). By including the photopolymerization initiator (E), the active energy ray-curable component (C) can be efficiently polymerized, and the polymerization curing time and the irradiation amount of the active energy ray can be reduced.

Examples of the photopolymerization initiator (E) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl] -2-morpholino-propane-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthiazolone, 2-ethylthiazolone, 2-chlorothiazolone, 2,4-dimethylthiazolone, 2,4-diethylthiazolone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoate, oligo[2-hydroxy-2-methyl-1 [4-(1-methylvinyl)phenyl]acetone], 2,4,6-trimethylbenzyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzyl)-phenylphosphine oxide, etc. These materials may be used alone or in combination of two or more.

Among the above, phosphine oxide-based photopolymerization initiators are preferred, which are easily decomposed even when irradiated with ultraviolet rays through a plastic plate containing an ultraviolet absorber and can easily and reliably cure the adhesive. Specifically, 2,4,6-trimethylbenzyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzyl)-phenylphosphine oxide, etc. are preferred.

The lower limit of the content of the photopolymerization initiator (E) in the adhesive composition P is preferably 0.1 parts by mass or more, particularly preferably 1 part by mass or more, and more preferably 5 parts by mass or more, relative to 100 parts by mass of the active energy ray-curable component (C). Furthermore, the upper limit is preferably 30 parts by mass or less, particularly preferably 20 parts by mass or less, and more preferably 12 parts by mass or less.

(1-6) Various additives In the adhesive composition P, various additives commonly used in acrylic adhesives may be added as needed, such as silane coupling agents, rust inhibitors, UV absorbers, antistatic agents, thickeners, antioxidants, light stabilizers, softeners, refractive index adjusters, etc. In addition, the additives constituting the adhesive composition P do not include the polymerization solvent and diluent described later.

The adhesive composition P preferably contains the silane coupling agent mentioned above. In this way, whether the adherend is a plastic plate or a glass component, the adhesion to the adherend can be improved, and the step compliance and blister resistance under high temperature and high humidity conditions become more excellent.

The silane coupling agent is preferably an organic silicon compound having at least one alkoxysilyl group in the molecule, having good miscibility with the (meth)acrylate polymer (A) and having light transparency.

Examples of such silane coupling agents include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane, epoxy structure-containing silicon compounds such as 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-butylpropyltrimethoxysilane, and 3-butyltrimethoxysilane. A silicon compound containing an alkyl group such as propyltriethoxysilane, 3-alkylpropyldimethoxymethylsilane, a silicon compound containing an amine group such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or a condensate of at least one of the above and a silicon compound containing an alkyl group such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, etc. The above materials may be used alone or in combination of two or more.

The content of the silane coupling agent in the adhesive composition P is preferably 0.01 parts by mass or more, particularly preferably 0.05 parts by mass or more, and more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the (meth)acrylate polymer (A). Furthermore, this content is preferably 1.2 parts by mass or less, particularly preferably 0.8 parts by mass or less, and more preferably 0.4 parts by mass or less.

(2) Preparation of adhesive composition The adhesive composition P can be prepared by preparing a (meth)acrylate polymer (A), mixing the obtained (meth)acrylate polymer (A) with a crosslinking agent (B) and an active energy ray-curable component (C), and adding a photopolymerization initiator (E), an additive, etc. as required. In the case of the light-diffusing adhesive layer 111, light-diffusing particles (D) are further prepared.

The (meth)acrylate polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer using a general free radical polymerization method. The polymerization of the (meth)acrylate polymer (A) can be carried out using a polymerization initiator as required, and preferably by a solution polymerization method. However, the present invention is not limited thereto, and the polymerization can also be carried out without a solvent. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and the like, and a combination of two or more thereof can also be used.

Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of the azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane 1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), and 2,2'-azobis[2-(2-imidazolin-2-yl)propane].

Examples of the organic peroxide include benzoyl peroxide, tertiary butyl perbenzoate, isopropyl hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl) peroxydicarbonate, tertiary butyl peroxyneodecanoate, tertiary butyl peroxypivalate, (3,5,5-trimethylhexyl) peroxide, dipropionyl peroxide, and diacetyl peroxide.

In addition, in the above polymerization step, the weight average molecular weight of the obtained polymer can be adjusted by adding a chain transfer agent such as 2-hydroxyethanol.

After obtaining the (meth)acrylate polymer (A), a crosslinking agent (B), an active energy ray-hardening component (C), and a diluting solvent as required, light diffusion particles (D), a photopolymerization initiator (E), an additive, etc. are added to the solution of the (meth)acrylate polymer (A), and the mixture is fully mixed to obtain an adhesive composition P (coating solution) diluted with a solvent. In addition, if any of the above components is used in a solid form or precipitates after being mixed with other components in an undiluted state, the component may be dissolved or diluted in a diluting solvent alone before being mixed with other components.

As the above-mentioned diluting solvent, for example, aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methyl chloride and ethyl chloride, alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve solvents such as cellosolve can be used.

The concentration/viscosity of the coating solution prepared in the above manner is not particularly limited as long as it is within the coating range, and can be appropriately selected according to the situation. For example, the concentration of the adhesive composition P can be diluted to 10 to 60% by mass. In addition, when obtaining the coating solution, the addition of a diluting solvent is not a necessary condition, as long as the adhesive composition P has a coating viscosity, etc., it is not necessary to add a diluting solvent. In this case, the adhesive composition P is a coating solution in which the polymerization solvent of the (meth)acrylate polymer (A) is directly used as the diluting solvent.

(3) Formation of adhesive layer The light diffusion adhesive layer 111 and the transparent adhesive layer 112 in the present embodiment are preferably each composed of an adhesive obtained by crosslinking the adhesive composition P (coating layer). The crosslinking of the adhesive composition P is preferably performed by heat treatment. In addition, the heat treatment can also be used as a drying treatment when the diluent solvent is volatilized from the coating layer of the adhesive composition P applied to the desired object.

The heating temperature of the heat treatment is preferably 50 to 150° C., and particularly preferably 70 to 120° C. Furthermore, the heating time is preferably 10 seconds to 10 minutes, and particularly preferably 50 seconds to 2 minutes.

Furthermore, after the heat treatment, a curing period of about 1 to 2 weeks at room temperature (e.g., 23°C, 50% RH) can be set as required. If this curing period is required, the adhesive is formed after the curing period, and if the curing period is not required, the adhesive is formed after the heat treatment is completed.

Through the above-mentioned heat treatment (and curing), the (meth)acrylate polymer (A) can be well crosslinked through the crosslinking agent (B).

The composite adhesive layer 11 in this embodiment can be obtained by laminating the light diffusion adhesive layer 111 and the transparent adhesive layer 112. The lamination can be performed before or after each adhesive layer is cured. However, in order to further improve the adhesion between the light diffusion adhesive layer 111 and the transparent adhesive layer 112, it is preferred to perform the lamination before each adhesive layer is cured.

1-2. Peeling sheet The peeling sheets 12a and 12b protect the composite adhesive layer 11 before the adhesive sheet 1 is used, and are peeled off when the adhesive sheet 1 (composite adhesive layer 11) is used. In the adhesive sheet 1 according to this embodiment, one or both of the peeling sheets 12a and 12b are not absolutely necessary.

As the release sheets 12a and 12b, for example, polyethylene film, polypropylene film, polybutylene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene/(meth)acrylic acid copolymer film, ethylene/(meth)acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. can be used. Furthermore, crosslinked films of the above materials can also be used. In addition, laminated films of the above materials can also be used.

The peeling surfaces of the peeling sheets 12a and 12b (particularly the surfaces in contact with the composite adhesive layer 11) are preferably subjected to a peeling treatment. Examples of the peeling agent used for the peeling treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax peeling agents.

The thickness of the peeling sheets 12a and 12b is not particularly limited, but is generally about 20 to 150 μm.

2. Production of adhesive sheet In one example of producing the adhesive sheet 1, a coating solution of an adhesive composition P for forming a transparent adhesive layer 112 is applied to a peeling surface of a peeling sheet 12a, and a heat treatment is performed to allow the adhesive composition P to be thermally crosslinked to form a coating layer, thereby obtaining a peeling sheet 12a with a coating layer. Furthermore, a coating solution of an adhesive composition P for forming a light diffusion adhesive layer 111 is coated on the peeling surface of another peeling sheet 12b, and a heat treatment is performed to thermally crosslink the adhesive composition P to form a coating layer, thereby obtaining a peeling sheet 12b with a coating layer. Then, the peeling sheet 12a with a coating layer and the peeling sheet 12b with a coating layer are attached so that the two coating layers are in contact with each other. Here, a plurality of peeling sheets with coating layers can also be prepared, and the coating layers can be laminated in the desired number and in the desired lamination order. When a curing period is required, the composite adhesive layer 11 is formed by leaving it for a period of curing, and when a curing period is not required, the above-layered coating layer is directly used as the composite adhesive layer 11. In this way, the above-mentioned adhesive sheet 1 having the composite adhesive layer 11 of the laminate of the light diffusion adhesive layer 111 and the transparent adhesive layer 112 can be obtained. The conditions for the heat treatment and curing are as described above.

In addition, the coating layer for forming the transparent adhesive layer 112 and the coating layer for forming the light diffusion adhesive layer 111 may each be sandwiched between two peeling sheets, or one peeling sheet may be peeled off each when the coating layer for forming the transparent adhesive layer 112 and the coating layer for forming the light diffusion adhesive layer 111 are bonded together.

Examples of a method for applying the coating liquid of the adhesive composition P include bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[Optical laminate] An optical laminate according to an embodiment of the present invention includes an optical component, another optical component, and a cured composite adhesive layer for bonding the optical component and the other optical component to each other. The cured composite adhesive layer is obtained by curing the composite adhesive layer of the adhesive sheet according to the embodiment by irradiating it with active energy rays.

At least one of the above-mentioned one optical component and the other optical component may have a step difference (convex and concave) on the surface of the side bonded by the above-mentioned cured composite adhesive layer. In this case, it is preferred that the transparent adhesive layer of the cured composite adhesive layer contacts the step difference.

The optical multilayer according to this embodiment can be the display itself or a component constituting a part of the display. Furthermore, the present invention is not limited thereto and can also be applied to optical uses other than displays.

Examples of the display include a liquid crystal (LCD) display, a light emitting diode (LED) display, an organic electroluminescent (organic EL) display, and electronic paper. The display may also be a touch panel.

FIG2 shows a specific structure of an optical laminate according to an embodiment of the present invention. As shown in FIG2 , the optical laminate 2A of the present embodiment includes a first optical component 21 (one optical component), a second optical component 22 (another optical component), and a cured composite adhesive layer 11' located between the first optical component 21 and the second optical component 22 for bonding the first optical component 21 and the second optical component 22 to each other.

One of the first optical component 21 and the second optical component 22 may have a step on the surface of the side to be bonded by the cured composite adhesive layer 11'. In the embodiment shown in FIG2 , the first optical component 21 has a step due to the printed layer 23 on the surface of the composite adhesive layer 11' side.

The cured composite adhesive layer 11' in the display body 2A is formed by curing the composite adhesive layer 11 of the adhesive sheet 1 using active energy rays. The cured composite adhesive layer 11' in this embodiment is a laminate of a light diffusion adhesive layer 111 and a transparent adhesive layer 112, and the transparent adhesive layer 112 is located on the side in contact with the step generated by the printed layer 23.

The first optical component 21 is preferably a protective panel composed of other components such as a glass plate, a plastic plate, etc., and a laminate including the former. In this case, a frame-shaped printed layer 23 is usually formed on the side of the composite adhesive layer 11 of the first optical component 21.

The glass plate is not particularly limited, and examples thereof include chemically strengthened glass, alkali-free glass, quartz glass, sodium calcium glass, barium/strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate glass, etc. The thickness of the glass plate is not particularly limited, and is generally 0.1 to 5 mm, preferably 0.2 to 2 mm.

The plastic plate is not particularly limited, and examples thereof include acrylic plates, polycarbonate plates, etc. The thickness of the plastic plate is not particularly limited, but is generally 0.2 to 5 mm, and preferably 0.4 to 3 mm.

In addition, various functional layers (transparent conductive film, metal layer, silicon dioxide layer, hard coating layer, anti-glare layer, etc.) may be provided on one or both surfaces of the glass plate or plastic plate, or optical components may be laminated. Furthermore, the transparent conductive film and metal layer may be patterned.

The second optical component 22 is preferably an optical component to be attached to the first optical component 21, a display module (for example, a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescent (organic EL) module, etc.), an optical component that is a part of the display module, or a laminate that includes a display module.

Examples of the optical components include anti-scattering films, polarizing plates (polarizing films), polarizers, phase difference plates (phase difference films), viewing angle compensation films, brightness enhancement films, contrast enhancement films, liquid crystal polymer films, diffusion films, semi-transmissive reflective films, and transparent conductive films. Examples of the anti-scattering films include hard coating films formed by forming a hard coating layer on one side of a base film.

The material constituting the printing layer 23 is not particularly limited, and known printing materials can be used. The thickness of the printing layer 23, that is, the lower limit of the height of the step, is preferably 3 μm or more, more preferably 5 μm or more, particularly preferably 7 μm or more, and most preferably 10 μm or more. By setting the lower limit to the above value, it is possible to fully ensure the concealment of wires, etc. from the viewer's side. Furthermore, the upper limit is preferably 50 μm or less, more preferably 35 μm or less, particularly preferably 25 μm or less, and more preferably 20 μm or less. By setting the upper limit to the above value, it is possible to prevent the reduction in the compliance of the composite adhesive layer 11' to the step of the printing layer 23 after curing, and to better maintain the uniformity of light diffusion.

As an example of manufacturing the display 2A, one of the release sheets 12a of the adhesive sheet 1 is peeled off, and the transparent adhesive layer 112 exposed in the adhesive sheet 1 is attached to the surface of the first optical component 21 on the side where the printed layer 23 exists.

Thereafter, another peeling sheet 12b is peeled off from the composite adhesive layer 11 of the adhesive sheet 1, and the light diffusion adhesive layer 111 exposed in the adhesive sheet 1 is bonded to the second optical component 22. Furthermore, as another example, the bonding order of the first optical component 21 and the second optical component 22 may be changed.

Next, the composite adhesive layer 11 is irradiated with active energy rays to form a cured composite adhesive layer 11'. The active energy rays irradiated on the composite adhesive layer 11 are usually irradiated through either the first optical component 21 or the second optical component 22, preferably through the first optical component 21 as a protective panel.

The so-called active energy rays refer to electromagnetic waves or charged particle beams with energy quanta, and specifically, ultraviolet rays and electron beams can be listed. Among active energy rays, ultraviolet rays are particularly preferred because they are easy to handle.

Ultraviolet irradiation can be performed using a high-pressure mercury lamp, a fusion H lamp, a xenon lamp, etc., and the ultraviolet irradiation is preferably about 50 to 1000 mW/ ^cm2 , and is also preferably about 100 to 500 mW/ ^cm2 . Furthermore, the light intensity is preferably 50 to 10000 mJ/ ^cm2 , more preferably 200 to 7000 mJ/ ^cm2 , and particularly preferably 500 to 3000 mJ/ ^cm2 . On the other hand, electron beam irradiation can be performed using an electron beam accelerator, etc., and the electron beam irradiation is preferably about 10 to 1000 krad.

As shown in Fig. 3, a display body 2B according to another embodiment includes a backlight source 30, a cured composite adhesive layer 11 laminated on the backlight source 30, and a display portion 40 laminated on the cured composite adhesive layer 11. The backlight source 30 in this display body 2B corresponds to the first optical component, and the display portion 40 corresponds to the second optical component.

The backlight source 30 includes one or more substrates 31 and a plurality of light emitting bodies 32 disposed on the substrate 31. The backlight source 30 has projections and depressions due to the plurality of light emitting bodies 32.

The cured composite adhesive layer 11' in the display body 2B is formed by curing the composite adhesive layer 11 of the adhesive sheet 1 using active energy rays. The cured composite adhesive layer 11' in this embodiment is a laminate of a light diffusion adhesive layer 111 and a transparent adhesive layer 112, and the transparent adhesive layer 112 is located on the side that contacts the concave and convex parts of the light-emitting body 32. The plurality of light-emitting bodies 32 are sealed by the transparent adhesive layer 112 without gaps. In this way, the light-emitting body 32 can be protected from moisture.

The substrate 31 is not particularly limited, and a substrate commonly used for a backlight source can be used. The substrate 31 is usually a printed circuit board (PCB substrate; Printed Circuit Board).

The substrate 31 may be integrally formed so that a plurality of light emitting bodies 32 are mounted together, or may be separately formed so that one light emitting body 32 is mounted on one substrate 31. In the case of separate formation, each substrate 31 is usually fixed to a frame, a support, a housing, etc. In this embodiment, as shown in FIG. 3 , it is preferred that the substrate 31 is integrally formed so that a plurality of light emitting bodies 32 are mounted together.

A reflective layer may be formed on the surface of the substrate 31 on the side of the composite adhesive layer 11, or a reflective component may be provided. In this way, the brightness of the backlight source 30 can be effectively improved. The reflective layer and the reflective component may be made of known materials.

Examples of the light emitting body 32 include light emitting diodes (LEDs), laser diodes (LDs), organic electroluminescent elements, inorganic electroluminescent elements, etc. Among them, LEDs are preferred from the perspective of sealing properties of the composite adhesive layer 11' after curing, and mini LEDs or micro LEDs are particularly preferred.

The thickness of the light emitting body 32 is preferably 10 μm or more, more preferably 30 μm or more, particularly preferably 50 μm or more, and more preferably 80 μm or more. Furthermore, the thickness of the light emitting body 32 is preferably 300 μm or less, more preferably 150 μm or less, and more preferably 100 μm or less.

Furthermore, the width of the gap between adjacent light emitting bodies 32 is preferably 0.01 mm or more, particularly preferably 0.1 mm or more, and more preferably 0.5 mm or more. Furthermore, the width of the gap is preferably 100 mm or less, more preferably 10 mm or less, particularly preferably 4 mm or less, and more preferably 2 mm or less.

The shape of the light emitting body 32 is not particularly limited, and is generally a rectangular parallelepiped, a hemispherical body, etc. The size of the light emitting body 32 is also not particularly limited, but from the perspective of the sealing performance of the light emitting body, one side or diameter in a plan view is preferably 0.01 to 100 mm, more preferably 0.1 to 10 mm, particularly preferably 0.2 to 5 mm, and even more preferably 0.5 to 2 mm.

The light diffusion adhesive layer 111 in this embodiment diffuses the light emitted from the backlight source 30, thereby effectively suppressing the occurrence of brightness unevenness.

The display unit 40 may be, for example, a liquid crystal panel, but is not limited thereto, and may be, for example, a part of a component constituting a liquid crystal panel, or an optical component used together to increase or enhance the function of the liquid crystal panel (for example, a light diffusion plate or an ultraviolet absorption filter, etc.). The display unit 40 may adopt a known display component.

In addition, a sealing material may be provided between the backlight source 30 and the cured composite adhesive layer 11'. In this case, the surface of the sealing material opposite to the backlight source 30 often has irregularities, but even so, the irregularities can be absorbed by the transparent adhesive layer 112 of the cured composite adhesive layer 11'.

Furthermore, a desired optical component may be provided between the cured composite adhesive layer 11' and the display unit 40, or on the surface of the display unit 40 opposite to the cured composite adhesive layer 11'. Examples of the optical component include brightness enhancement films, contrast enhancement films, viewing angle compensation films, transparent conductive films, liquid crystal polymer films, semi-transmissive reflective films, and anti-scattering films.

In manufacturing the display 2B according to the present embodiment, for example, one of the release sheets 12a of the adhesive sheet 1 is peeled off, and the transparent adhesive layer 112 exposed in the adhesive sheet 1 is attached to the surface of the backlight source 30 on the side where the light emitting body 32 exists.

Thereafter, another peeling sheet 12b is peeled off from the composite adhesive layer 11 of the adhesive sheet 1, and the light diffusion adhesive layer 111 exposed in the adhesive sheet 1 is bonded to the display portion 40. Then, the composite adhesive layer 11 is irradiated with active energy rays to form a cured composite adhesive layer 11'. Alternatively, before bonding the display portion 40, the composite adhesive layer 11 is irradiated with active energy rays to form a cured composite adhesive layer 11' (after peeling off the peeling sheet 12b), and then bonded to the display portion 40. The irradiation conditions of the active energy rays are the same as those of the display body 2A.

As another example, the bonding sequence of the backlight source 30 and the display unit 40 may be changed.

The embodiments described above are recorded for easy understanding of the present invention and are not recorded for limiting the present invention. Therefore, it means that each element disclosed in the above embodiments also includes all design changes and equivalents within the technical scope of the present invention.

For example, one or both of the release sheets 12a and 12b in the adhesive sheet 1 may be omitted, and a desired optical component may be laminated instead of the release sheets 12a and/or 12b.

Furthermore, as shown in the adhesive sheet 1A in FIG4 , the composite adhesive layer 11 may be formed by laminating the transparent adhesive layer 112, the light diffusion adhesive layer 111, and the transparent adhesive layer 112 in this order. The adhesive sheet 1A is effective when either the first optical component or the second optical component has a step (convex and concave) on the side of the composite adhesive layer 11. For example, the adhesive sheet 1A is effective when either the first optical component or the second optical component is a liquid crystal panel.

The embodiments described above are recorded for easy understanding of the present invention and are not recorded for limiting the present invention. Therefore, it means that each element disclosed in the above embodiments also includes all design changes and equivalents within the technical scope of the present invention.

For example, either the peeling sheet 12a or 12b in the adhesive sheet 1 may be omitted. [Example]

Hereinafter, the present invention will be described in more detail through examples, etc. However, the scope of the present invention is not limited to these examples, etc.

[Production Example 1] (Production of a light-diffusing adhesive sheet) 1. Preparation of (meth)acrylate polymer 65 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of isobornyl acrylate, 5 parts by mass of N-acryloylmorpholine and 15 parts by mass of 2-hydroxyethyl acrylate were copolymerized by solution polymerization to prepare a (meth)acrylate polymer (A). The molecular weight of the (meth)acrylate polymer (A) was measured by the method described later, and the weight average molecular weight (Mw) was 500,000.

2. Preparation of adhesive composition 100 parts by weight of the (meth)acrylate polymer (A) obtained in step 1 above (converted to solid content, the same applies hereinafter), 0.20 parts by weight of trihydroxymethylpropane-modified toluene diisocyanate (produced by Toyo Chemical Co., Ltd., product name "BHS8515") as a crosslinking agent (B), and 5.2 parts by weight of ε-caprolactone-modified tris(2-acryloyloxyethyl) isocyanurate (produced by Shin-Nakamura Chemical Co., Ltd., product name "NKester A-9300-1CL"), 5.0 parts by weight of particles composed of silicone resin (a silicon-containing compound having a structure intermediate between inorganic and organic) as light diffusion particles (D) (produced by Maitu Advanced Materials Japan Co., Ltd., product name "Tospearl 145", average particle size: 4.5μm), 0.5 parts by weight of 2,4,6-trimethylbenzyl-diphenyl-phosphine oxide as a photopolymerization initiator (E), and 0.2 parts by weight of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent were mixed and stirred thoroughly, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

Here, the formulations of the adhesive composition (values converted to solid content) when the (meth)acrylate polymer (A) is set to 100 parts by mass (values converted to solid content) are shown in Table 1. In addition, the details of the abbreviations and the like described in Table 1 are as follows. [(Meth)acrylate polymer (A)] 2EHA: 2-ethylhexyl acrylate IBXA: Isobornyl acrylate ACMO: N-acryloylmorpholine HEA: 2-hydroxyethyl acrylate BA: n-butyl acrylate AA: acrylic acid [Crosslinking agent (B)] TDI type: trihydroxymethylpropane-modified toluene diisocyanate (manufactured by Toyo Chemical Co., Ltd., product name "BHS8515") XDI type: trihydroxymethylpropane-modified xylene diisocyanate ( =Manufactured by Soken Chemical Co., Ltd., product name "TD-75") Epoxy: 1,3-bis(N,N-diglycerylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name "TETRAD-C") [Light-diffusing particles (D)] D1: Particles composed of a silicone resin (a silicon-containing compound with a structure between inorganic and organic) with an average particle size of 4.5μm (manufactured by Maitu Advanced Materials Japan Co., Ltd., product name "Tospearl 145", refractive index: 1.43) D2: Microparticles composed of silicone resin (a silicon-containing compound with a structure between inorganic and organic) with an average particle size of 2.0μm (produced by Maitu Advanced Materials Japan, product name "Tospearl 120", refractive index: 1.43) D3: True spherical polymethyl methacrylate-polystyrene copolymer microparticles with an average particle size of 4.0μm (produced by Sekisui Chemical Industry Co., Ltd., product name "XX-30LA", refractive index: 1.56)

3. Preparation of light-diffusing adhesive sheet The coating solution of the adhesive composition obtained in step 2 was applied to the peeling-treated surface of a heavy-peel peeling sheet (manufactured by Lintec, product name "SP-PET752150") obtained by peeling one side of a polyethylene terephthalate film with a silicone peeling agent using a doctor blade coater, and then the coating layer was heat-treated at 90°C for 1 minute to form a coating layer (thickness: 50μm).

Next, the coating layer on the heavy-peel release sheet obtained above and a light-peel release sheet (produced by Lintec Corporation, product name "SP-PET38131") obtained by peeling one side of a polyethylene terephthalate film with a silicone-based peeling agent were bonded to each other in such a manner that the peeling-treated surface of the light-peel release sheet was in contact with the coating layer, thereby producing an adhesive sheet having a structure of heavy-peel release sheet/light-diffusing adhesive layer (a) coating layer (thickness: 50 μm)/light-peel release sheet.

The thickness of the adhesive layer is a value measured using a constant pressure thickness gauge (manufactured by TECLOCK, product name "PG-02") in accordance with JIS K7130.

[Production Examples 2 to 7, 9 to 10] (Production of light-diffusing adhesive sheets) Except that the types and proportions of the monomers constituting the (meth)acrylate polymer (A), the weight average molecular weight (Mw) of the (meth)acrylate polymer (A), the amount of the crosslinking agent (B), the amount of the active energy radiation curable component (C), the type and amount of the light-diffusing fine particles (D), the amount of the photopolymerization initiator (E), and the amount of the silane coupling agent were changed to those shown in Table 1, the same method as in Production Example 1 was followed to produce a light-diffusing adhesive layer (b) (Production Example 2), a light-diffusing adhesive layer (c) (Production Example 3), a light-diffusing adhesive layer (d) (Production Example 4), and a light-diffusing adhesive layer (e) (Manufacturing Example 5), a light diffusion adhesive layer (f) (Manufacturing Example 6), a light diffusion adhesive layer (g) (Manufacturing Example 7), a light diffusion adhesive layer (i) (Manufacturing Example 9), and a light diffusion adhesive layer (j) (Manufacturing Example 10) of the light diffusion adhesive sheet. However, with respect to the light diffusion adhesive sheet having the light diffusion adhesive layer (j) (Manufacturing Example 10), under the same conditions as those of Experimental Example 1 described later, the light diffusion adhesive layer was irradiated with active energy rays (ultraviolet rays) via a light peeling type peeling sheet, so that the light diffusion adhesive layer was pre-hardened.

[Production Example 8] (Production of a transparent adhesive sheet) Except that the types and ratios of the monomers constituting the (meth)acrylate polymer (A), the weight average molecular weight (Mw) of the (meth)acrylate polymer (A), the amount of the crosslinking agent (B), the amount of the active energy radiation curable component (C), the amount of the light diffusion particles (D) (not blended), the amount of the photopolymerization initiator (E), and the amount of the silane coupling agent were changed to those shown in Table 1, a transparent adhesive sheet having a transparent adhesive layer (h) (Production Example 8) was produced in the same manner as in Production Example 1. In addition, regarding the transparent adhesive sheet having the transparent adhesive layer (h) used in Example 9, under the same conditions as in Experimental Example 1 described later, the transparent adhesive layer was pre-hardened by irradiating active energy rays (ultraviolet rays) through a light-peel type peeling sheet.

The weight average molecular weight (Mw) is the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC) under the following conditions (GPC measurement). ＜Measurement conditions＞ ・GPC measurement device: HLC-8020 manufactured by Tosoh Corporation ・GPC column (passed in the following order): manufactured by Tosoh Corporation TSK guard column HXL-H TSK gel GMHXL (x2) TSK gel G2000HXL ・Measurement solvent: tetrahydrofuran ・Measurement temperature: 40°C

[Example 1] A light-peelable release sheet was peeled off from the light-diffusing adhesive sheet produced in Production Example 1 to expose the coating layer of the light-diffusing adhesive layer (a). Furthermore, a light-peelable release sheet was peeled off from the transparent adhesive sheet produced in Production Example 8 to expose the coating layer of the transparent adhesive layer (g). A coating layer of the transparent adhesive layer (g) was laminated on the coating layer of the light-diffusing adhesive layer (a), and cured at 23°C and 50% RH for 7 days. In this way, an adhesive sheet consisting of a re-peelable release sheet/a light diffusion adhesive layer (a) (50 μm)/a transparent adhesive layer (g) (50 μm)/a re-peelable release sheet (light diffusion adhesive layer + transparent adhesive layer = composite adhesive layer) can be manufactured.

[Examples 2 to 9, Comparative Examples 1 to 3] The adhesive sheet was produced in the same manner as in Example 1 except that the types of the light diffusion adhesive layer and the transparent adhesive layer were changed as shown in Table 2. In addition, in Table 2, for convenience, the transparent adhesive layer is also recorded in the column of the light diffusion adhesive layer of Comparative Example 1, and the light diffusion adhesive layer is also recorded in the column of the transparent adhesive layer of Comparative Examples 2 and 3.

[Test Example 1] (Measurement of gel fraction) The adhesive sheets (after curing) produced in each manufacturing example and the adhesive sheets obtained in the embodiment and comparative example were cut into a size of 80 mm × 80 mm, and the adhesive layer of the adhesive sheet was wrapped in a polyester net (mesh size of 200). The mass was measured with a precision balance, and the mass of the adhesive alone was calculated by deducting the mass of the polyester net itself. The mass at this time is set as M1.

Next, the adhesive coated in the above polyester mesh was immersed in ethyl acetate at room temperature (23°C) for 24 hours. After that, the adhesive was taken out and air-dried for 24 hours in an environment with a temperature of 23°C and a relative humidity of 50%, and further dried in an oven at 80°C for 12 hours. After drying, its mass was weighed with a precision balance, and the mass of the adhesive alone was calculated by deducting the mass of the above polyester mesh itself. The mass at this time is set as M2. The gel fraction (%) is expressed as (M2/M1)×100. In this way, the gel fraction of the adhesive (before UV irradiation) can be derived. The results are shown in Table 2.

On the other hand, the adhesive layer of the adhesive sheets (after curing) produced in each manufacturing example and the adhesive sheets obtained in the examples and comparative examples (except for manufacturing example 10 and comparative example 3) was irradiated with active energy rays (ultraviolet rays; UV) through a light peeling type peeling sheet under the following conditions, so that the adhesive layer was cured to form a cured adhesive layer. The gel fraction (after UV irradiation) of the adhesive of this cured adhesive layer was derived in the same manner as above. The results are shown in Table 2.

＜Active energy ray irradiation conditions＞ ・High-pressure mercury lamp was used ・Illuminance was 200mW/cm ² , luminous intensity was 1000mJ/cm ²・UV illuminance and light meter "UVPF-A1" manufactured by Eye Graphics was used

[Test Example 2] (Measurement of storage modulus) The peeled sheets were peeled from the adhesive sheets (after curing) produced in each manufacturing example and the adhesive sheets obtained in the embodiment and the comparative example, and multiple layers were stacked so that the adhesive layer had a thickness of 800μm. A cylinder with a diameter of 8mm (height of 800μm) was punched out from the obtained laminate of the adhesive layer and used as a sample.

Based on the JIS K7244-6 standard, the storage modulus (GD1, GT1, G1) of the above samples at 23°C (before UV irradiation; MPa) was measured using a viscoelasticity measuring device (manufactured by PHYSICA, product name "MCR300") using the torsional shear method under the following conditions. The results are shown in Table 2. Measurement frequency: 1 Hz Measurement temperature: 23°C

Furthermore, under the same conditions as in Experimental Example 1, the same samples as above (except for Preparation Example 10 and Comparative Example 3) were irradiated with active energy rays (ultraviolet rays; UV) to cure the adhesive, thereby obtaining samples after active energy ray irradiation. For the obtained samples after active energy ray irradiation, the storage modulus (GD2, GT2, G2) at 23°C was measured in the same manner as the samples before active energy ray irradiation (after UV irradiation, MPa). The results are shown in Table 2.

Furthermore, the ratio of the storage modulus (GD2, GT2, G2) after active energy ray irradiation to the storage modulus G1 (GD1, GT1, G1) before active energy ray irradiation was calculated, which is the storage modulus change rate (ΔGD, ΔGT, ΔG’). The results are shown in Table 2.

[Test Example 3] (Measurement of haze value) The composite adhesive layer of the adhesive sheet produced in the embodiment and the comparative example was attached to glass as a sample for measurement. After background measurement using glass, the haze value (%) of the sample for measurement was measured using a haze meter (manufactured by Nippon Denshoku Industries, product name "SH-7000") in accordance with JIS K7136:2000. The results are shown in Table 2.

[Test Example 4] (Measurement of total light transmittance) The composite adhesive layer of the adhesive sheet produced in the embodiment and the comparative example was attached to glass as a measurement sample. After background measurement using glass, the total light transmittance (%) of the above measurement sample was measured using a haze meter (manufactured by Nippon Denshoku Industries, product name "SH-7000") in accordance with JIS K7361-1:1997. The results are shown in Table 2.

[Test Example 5] (Measurement of Adhesive Force) The releasable release sheet located on the side of the light diffusing adhesive layer was peeled off from the adhesive sheet obtained in the embodiment and the comparative example, and the exposed light diffusing adhesive layer was bonded to the easy bonding layer of a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name "PET A4300"), thickness: 100μm) having an easy bonding layer, thereby obtaining a laminate of releasable release sheet/composite adhesive layer/PET film. The obtained laminate was cut into a width of 25mm and a length of 100mm.

In an environment of 23°C and 50% RH, the heavy peel release sheet on the side of the transparent adhesive layer was peeled off from the above laminate, and the exposed transparent adhesive layer was attached to sodium calcium glass (manufactured by Nippon Sheet Glass Co., Ltd.), and pressurized at 0.5MPa and 50°C for 20 minutes using an autoclave manufactured by Kurihara Seisakusho Co., Ltd. After that, it was left at 23°C and 50% RH for 24 hours and used as a sample. Then, the adhesion (transparent adhesive layer before UV irradiation; N/25mm) was measured using a tensile tester (manufactured by Orientec, product name "TENSILON") at a peeling speed of 300mm/min and a peeling angle of 180 degrees. Except for the conditions described here, the rest was measured in accordance with JIS Z0237:2009.

Next, under the same conditions as in Experimental Example 1, the above sample was irradiated with active energy rays through the PET film, so that the composite adhesive was hardened to form a hardened composite adhesive layer. The adhesive force of the hardened composite adhesive layer was measured in the same manner as above (transparent adhesive layer after UV irradiation; N/25mm). The results are shown in Table 2.

Furthermore, the adhesion of the light diffusion adhesive layer before UV irradiation (light diffusion adhesive layer before UV irradiation; N/25mm) and the adhesion of the light diffusion adhesive layer after UV irradiation (transparent adhesive layer after UV irradiation; N/25mm) were measured in the same manner as above. The results are shown in Table 2.

[Test Example 5] (Evaluation of step conformity) On the surface of a glass plate (manufactured by NSG Precision, product name "Corning Glass Eagle XG", 90 mm long × 50 mm wide × 0.5 mm thick), a frame-shaped (outer shape: 90 mm long × 50 mm wide, 5 mm wide) UV curable ink (manufactured by Teikoku Ink Co., Ltd., product name "POS-911 ink") was screen-printed. Then, the printed UV curable ink was cured by irradiation with UV rays (80 W/ ^cm2 , 2 metal halide lamps, lamp height 15 cm, conveyor belt speed 10 to 15 m/min), thereby producing a glass plate with steps (step height: 5 μm, 10 μm, 15 μm and 20 μm) generated by printing.

The heavy peelable release sheet on the side of the light diffusion adhesive layer was peeled off from the adhesive sheet obtained in the embodiment and the comparative example, and the exposed light diffusion adhesive layer was bonded to a sodium calcium glass plate (manufactured by Nippon Sheet Glass Co., Ltd., thickness: 0.7 mm). Next, the heavy peelable release sheet on the side of the transparent adhesive layer was peeled off to expose the transparent adhesive layer. Then, the above-mentioned laminate was pressed onto each of the glass plates with a step using a laminating press (manufactured by Fujipla Co., Ltd., product name "LPD3214") so that the composite adhesive layer covered the entire surface of the frame-shaped printing. After that, it was sterilized by high pressure at 50°C and 0.5 MPa for 30 minutes, and then placed at normal pressure, 23°C, and 50% RH for 24 hours.

Next, under the same conditions as in Experimental Example 1, the composite adhesive was cured into a cured composite adhesive layer by irradiating active energy rays through the sodium calcium glass plate (except for Comparative Example 3). Next, it was stored under wet and hot conditions of 85°C and 85% RH for 72 hours (durability test). After that, the step compliance was evaluated according to the following standards. The results are shown in Table 2. ◎: Conforms to all height steps without bubbles, floating or peeling. ○: Conforms to all height steps before the durability test, but bubbles, floating or peeling appear at steps above 15μm in height after the durability test. ×: Bubbles, floating or peeling appear from the beginning of the durability test.

[Test Example 6] (Evaluation of blister resistance) The heavy peelable release sheet on the side of the transparent adhesive layer was peeled off from the adhesive sheet obtained in the embodiment and the comparative example, and the exposed transparent adhesive layer was attached to the side of a plastic sheet (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name "Iupilon sheet MR58U", thickness: 0.7 mm, containing an ultraviolet absorber) on which a PMMA layer was laminated on a PC sheet, thereby obtaining a plastic sheet with a composite adhesive layer.

The heavy peelable release sheet on the side of the light diffusion adhesive layer was peeled off from the plastic plate with the composite adhesive layer obtained above, and the plastic plate was attached to a sodium calcium glass plate (manufactured by Nippon Sheet Glass Co., Ltd., thickness: 0.7 mm) with a size of 70 mm × 150 mm through the exposed light diffusion adhesive layer. After that, it was sterilized by high pressure at 50°C and 0.5 MPa for 30 minutes, and then left at normal pressure, 23°C, and 50% RH for 24 hours.

Next, under the same conditions as in Experimental Example 1, the composite adhesive layer was irradiated with active energy rays through a sodium calcium glass plate, so that the composite adhesive was cured to form a cured composite adhesive layer (except for Comparative Example 3). In this way, a laminate (70 mm × 150 mm) in which a plastic plate and a glass plate were bonded together by the cured composite adhesive layer was obtained.

The laminate was stored at 85°C and 85% RH for 72 hours. After that, the state of the interface between the cured composite adhesive layer and the adherend (plastic plate, glass plate) was visually confirmed, and the blister resistance was evaluated according to the following criteria. The results are shown in Table 2. ◎: No bubbles, floating or peeling. ○: Tiny bubbles appeared. ×: Bubbles, floating or peeling appeared overall.

[Test Example 7] (Evaluation of brightness unevenness suppression) A liquid crystal display device of a flat panel terminal (manufactured by Apple, product name "iPad (registered trademark)", resolution: 264ppi) was prepared as a surface light source. The surface of this liquid crystal display device was covered with a stainless steel mesh to obtain a virtual point light source. In addition, the conditions of the above-mentioned liquid crystal display device and the details of the stainless steel mesh are as follows. <LCD display device> Display color: white Brightness setting: maximum Pixel value: 980x980 <Stainless steel mesh> Stainless steel type: SUS316 Weaving method: plain weave Wire diameter: 50μm Mesh: 204μm Opening rate: 64.5% Number of grids: 100 (/25.4mm)

On the other hand, the surface of the light diffusing adhesive layer side of the adhesive sheet obtained in the example and the comparative example was bonded to a sodium calcium glass plate (manufactured by Nippon Sheet Glass Co., Ltd., thickness: 0.7 mm), and the obtained laminate was used as a sample.

The sample was placed on the virtual point light source so that the side of the transparent adhesive layer was in contact with the virtual point light source, and the metal wire was confirmed to be visible from 30 cm above the sample for sensory evaluation. Based on the results, the brightness unevenness suppression was evaluated according to the following standards. The results are shown in Table 2. ◎: The metal wire was shielded and the brightness distribution was uniform. ○: The metal wire was visible if the visual observation was focused, but the brightness distribution was roughly uniform. ×: The metal wire was clearly visible and the brightness distribution was uneven.

[Table 1]

[Table 2]

From Table 2, it can be seen that the adhesive sheet manufactured in the embodiment has excellent step compliance and excellent brightness unevenness suppression. Furthermore, the adhesive sheets manufactured in Examples 1 to 8 also have excellent blister resistance. [Industrial Applicability]

The adhesive sheet and optical laminate according to the present invention can be suitably used for parts and devices that require uniform light diffusion and durability, especially liquid crystal displays and the like.

1,1A: Adhesive sheet 11: Composite adhesive layer 111: Light diffusion adhesive layer 112: Transparent adhesive layer 12a,12b: Peeling sheet 2A,2B: Optical laminate 11': Cured composite adhesive layer 21: First optical component 22: Second optical component 23: Printing layer 30: Backlight source 31: Substrate 32: Light emitter 40: Display unit

[FIG. 1] is a cross-sectional view of an adhesive sheet according to an embodiment of the present invention. [FIG. 2] is a cross-sectional view of an optical laminate according to an embodiment of the present invention. [FIG. 3] is a cross-sectional view of an optical laminate according to another embodiment of the present invention. [FIG. 4] is a cross-sectional view of an adhesive sheet according to another embodiment of the present invention.

1: Adhesive sheet

11: Composite adhesive layer

111: Light diffusion adhesive layer

112: Transparent adhesive layer

12a,12b: Peeling film

Claims (15)

An adhesive sheet includes a composite adhesive layer having a light-diffusing adhesive layer containing light-diffusing particles and a transparent adhesive layer not containing light-diffusing particles, wherein either the light-diffusing adhesive layer or the transparent adhesive layer is composed of an active energy ray-curable adhesive. The adhesive sheet as described in claim 1, wherein the haze value of the composite adhesive layer is greater than 40% and less than 99%. The adhesive sheet as described in claim 1, wherein the storage modulus G1 of the composite adhesive layer at 23°C is greater than 0.001 MPa and less than 0.2 MPa. The adhesive sheet as described in claim 1, wherein the storage modulus G2 of the composite adhesive layer at 23°C after irradiation with active energy rays is greater than 0.08 MPa and less than 10 MPa. The adhesive sheet as described in claim 1, wherein the storage modulus change rate △G' is the ratio of the storage modulus G2 of the aforementioned composite adhesive layer at 23°C after irradiation with active energy rays to the storage modulus G1 of the aforementioned composite adhesive layer at 23°C, and the ratio is greater than 1.1 and less than 100. The adhesive sheet as described in claim 1, wherein the adhesive force of the transparent adhesive layer in the adhesive sheet to the sodium calcium glass is greater than 20N/25mm and less than 80N/25mm. The adhesive sheet as described in claim 1, wherein the adhesive force of the transparent adhesive layer in the adhesive sheet to sodium calcium glass after irradiation with active energy rays is greater than 20N/25mm and less than 80N/25mm. The adhesive sheet as described in claim 1, wherein the adhesion of the light diffusion adhesive layer in the adhesive sheet to the sodium calcium glass is greater than 1N/25mm and less than 60N/25mm. An adhesive sheet as described in claim 1, wherein the adhesion of the light diffusion adhesive layer in the adhesive sheet to sodium calcium glass after irradiation with active energy rays is greater than 10N/25mm and less than 60N/25mm. The adhesive sheet as described in claim 1, wherein the thickness of the composite adhesive layer is greater than 20 μm and less than 1000 μm. The adhesive sheet as described in claim 1, wherein the thickness of the light diffusion adhesive layer is greater than 10 μm and less than 500 μm. The adhesive sheet as described in claim 1, wherein the thickness of the transparent adhesive layer is greater than 10 μm and less than 500 μm. The adhesive sheet as described in claim 1 includes two peeling sheets, wherein the composite adhesive layer is sandwiched between the peeling sheets and contacts the peeling surfaces of the two peeling sheets. An optical laminate comprising an optical component, another optical component, and a cured composite adhesive layer for bonding the optical component and the other optical component to each other, wherein the cured composite adhesive layer is obtained by curing the composite adhesive layer of the adhesive sheet described in any one of claims 1 to 13 with active energy rays. An optical laminate as described in claim 14, wherein at least one of the optical component and the other optical component has a concave-convex surface on the side bonded by the cured composite adhesive layer, and the transparent adhesive layer of the cured composite adhesive layer contacts the concave-convex surface.